Brake proportioning valves



March 19, 1968 R. E. DOERFLER 3 ,37 ;765

BRAKE PROPORTIONING VALVES I Filed Oct. 22, 1965 FIG.

BY ROGER E. DOERFLER ATTYS.

United States Patent Office 8 Claims. (Cl. 137-494) ABSTRACT OF THEDISCLOSURE Apparatus for proportioning hydraulic brake pressure to awheel pair of a motor vehicle, theapparatus including a spool mounted inthe bore of a body having an inlet and outlet end. The spool, responsiveto an increase in pressure at the inlet end, moves towards the inletuntil it seals off the inlet pressure and prevents further communicationbetween the inlet and outlet until an increased pressure is placed onthe inlet end of the spool. Thereafter pressure increases to the wheelpair at a fixed percentage of the inlet pressure increase rate. Theimprovement includes a novel check valve for inhibiting flow or pressurecommunication between the inlet and outlet when the spool is sealing theinlet, and to permit flow upon release of pedal pressure from the mastercylinder.

This application is a continuation-in-part of application S.N. 469,271,filed on July 2, 1965.

The present invention relates to a proportioning valve for automotivebrake systems and more particularly to improvements in a proportioningvalve which provides automatically a programmed but variabledifferential hydraulic pressure between the front and rear brakes of ahydraulic brake system.

As set forth in the above-mentioned copending application, conventionalautomotive braking systems for vehicles having front mounted enginesrequire differential braking forces in order that the vehicle may bestopped smoothly and that the brakes themselves may wear evenly. Asweight distribution in most front engine vehicles is approximately60:40, the brakes mounted on the front wheels of the vehicle mustprovide 60% of the total braking force while the brakes mounted on therear wheels must afiord 40% of the braking force. In the conventionalmotor vehicle this is accomplished by providing 60% of the total brakearea on the front brake shoes and 40% of the total brake area on therear brake shoes. In this manner equal static hydraulic pressure may beapplied to the rear and forward brake cylinders while the differentialareas compensate for the differences in weight distribution.

In certain instances it is desirable to combine, in a hybrid type brakesystem, disc type brakes on the wheels of the vehicle carrying moreweight (typically the front wheels), with conventional shoe type brakeson the rear of the motor vehicle. As is well known, the disc brakeallows an increase in applied braking pressure and thus an increase inthe rolling friction of the tires against the surface upon which theyare riding, without suffering the deleterious effects of brake lockwhich occurs with shoe type brakes. Further, with disc type brakes, evenwith excessive usage, brake fade is almost non-existent. However, as maybe imagined hybrid brake systems combining disc and shoe type brakescreate serious problems as to differential braking pressures betweenthat required by the shoe and disc brake. It has been found that simplyproviding a difference in brake area between the disc and shoe typebrakes is not a practical solution and thusit becomes necessary toprovide a valving system which permits increased pressure to be appliedto the disc type brakes, in certain instances, above that applied to theshoe type brakes, and on a proportional basis.

In the afore-mentioned copending application, a proportioning valve isdescribed which proportions hydraulic pressure to one of brake systemswhen it is desired to increase the pressure on the other system tocompensate for different types of systems located in the front or rearand/or differences in weight distribution in the vehicle to which it isconnected.

In the proportioning valve of the copending application a valve body isillustrated having a hydraulic fluid inlet and a hydraulic outlet with aspool which is movable between a first position adjacent the outlet anda second position adjacent the inlet. This valve is also provided withconnecting means located interiorly of the spool to permit hydrauliccommunication between the outlet and the inlet when the spool is in itsfirst position and sealing means such as a check valve to seal theconnecting means when the spool is in its second position. As described,the spool itself has a proportioning ratio between the end thereofexposed to the outlet and the end exposed to the inlet such that thehydraulic force exerted on the spool at the outlet is greater per unitarea than the hydraulic force exerted upon the spool at the inlet. Inthis manner, the spool moves from its first position to the secondposition.

In the valve as above-described a problem is encountered in the checkvalve which sealed the connecting means when the spool moves to thesecond position. The problem encountered is caused by mis-alignment ofthe check valve due to dirt or impurities which occur in the hydrauliclines, and deposit in the seat of the check valve. In this mannercommunication between the outlet and the inlet is permitted, regardlessof the position of the valve spool, thus defeating the very purpose ofthe valve.

In view of the above it is a principal object of the present inventionto provide a novel check valve particularly adapted for use in ahydraulically operated proportioning valve such as that defined in theafore-mentioned copending application.

Another object of the present invention is to provide a check valvewhich will automatically position itself to seal the connecting meansinteriorly of the spool at the proper time in the valves sequentialoperation.

Still another object of the present invention is to provide a checkvalve which will rotate to a new seating position upon release andre-application of hydraulic pressure.

Other objects and a fuller understanding of the invention may be had byreferring to the following specifica tion taken in conjunction with theaccompanying claims and drawing in which:

FIG. 1 is a schematic diagram of a brake system having conventional shoeand drum, rear mounted brakes, and conventional front mounted discbrakes and incorporating a proportioning valve constructed in accordancewith the present invention;

FIG. 2 is an enlarged fragmentary sectional view of the proportioningvalve illustrated in FIG. 1;

FIG. 3 is an enlarged fragmentary sectional View of a portion of theproportioning valve illustrated in FIG. 2;

FIG. 4 is a sectional view taken along line 44 of FIG. 3; and

FIG. 5 is a development of a portion of the valve shown in FIGS. 2, 3and 4.

For ease of reading, the following specification is broken into threesections, Introduction, The Proportioning Valve and The Check Valve.

In trod ucti on Referring now to the drawings, and especially FIG. 1,. abrake system 10 is schematically illustrated therein,

Patented Mar. 19, 1968 comprising, in the present instance, caliper typedisc brakes 11 mounted on front Wheels 12, and shoe type brakes 13mounted on rear wheels 14. Connecting the shoe brakes 13 is hydraulicpiping 15 which emanates from a proportioning valve embodying interiorlythereof novel sealing means constructed in accordance with the presentinvention. Connecting the disc brakes 11 is hydraulic piping 16emanating from a T 17 interconnecting the proportioning valve 20 and aconventional master cylinder 18. As is usual, the master cylinder 18 isactuated by a linkage 19 and the customary foot pedal 19a.

The proportioning valve The proportioning valve 20, with the exceptionof the novel sealing means or check valve, is substantially as set forthin the aforementioned copending application, but is set forthhereinafter for purposes of clarity.

The proportioning valve 20 is operative to proportion and program thesequential application of hydraulic pressure to the shoe type brakes 14,solely by hydraulic imbalance. To this end, the valve 20 comprises avalve body 21 having a hydraulic fiuid inlet 22 and at least onehydraulic fluid outlet 23. As illustrated in FIG. 1, the outlet 23 isconnected to the rear shoe brakes 13 while the inlet 22 is connectedthrough the T 17 to the master cylinder 18. In the present instance, theinlet and outlet connections to the body 21 comprise nipples 22a and 23arespectively. Between the inlet 22 and the outlet 23 is a bored hole 25having slidingly mounted therein a spool 26, the spool having an inletend 26a and an outlet end 26b and movable between a first positionadjacent the outlet 23 (i.e. with reference to FIG. 2), to the left anda second position to the right. Adjacent the inlet 22 and mounted withinthe body is a sleeve 27 having a hollow interior forming a first chamber28, communicative at one end 29 through a passage 30 with the inlet 22,and circumscribing the inlet end 26a of the spool 26. To providecommunication between the inlet 22 and the outlet 23 so that hydraulicpressure applied at the inlet may also be applied at the outlet, thespool 26 contains means defining an aperture or conduit 32 connectingthe chamber 28 and the outlet 23 via radially extending openings 32a andan axial conduit extension 3211.

At the outlet end 26b of the spool 26 are a pair of spaced annularshoulders 33 and 34 having an annular seal 35a, such as an O-ring,mounted therebetween. The shoulders 33 and 34 are positioned in a secondchamber 36 formed in the body 21 and having an axially spaced radiallyextending end wall 37, the forward end of the nipple 23a forming theother end wall 38. A second seal 35b is positioned adjacent the wall 37and sealingly engages the exterior of the spool 26. Between the end wall37 and the first shoulder 33 of the spool 26 is biasing means, in thepresent instance a conical compression spring 39 which tends, prior tothe application of hydraulic pressure to the spool through the inlet 22,to keep the spool in its first position, i.e. towards the left.

In order to permit axial movement of the spool 26 between its first andsecond positions, solely by hydraulic imbalance, and to permit themovement of the spool toovercome the compression of the spring 39, thearea of the second shoulder 34, exposed to the hydraulic fluid at theoutlet 23 and designated A-1 for purposes of identification, is greaterthan the area A-2 exposed to bydraulic pressure from the inlet 22. Thus,upon receipt of suflicient pressure to overcome the spring force, thespool moves to the right until the resultant hydraulic force exertedagainst the area A-1 is equal to the sum of the resultant hydraulicforce exerted against the area A-2 and the spring force. At thisposition a state of balance will occur.

At a predetermined pressure it is desirable to lower the rate at whichthe pressure applied to the rear shoe brakes 13 through the outlet 23increases, while maintaining the pressure rate increase to the forwarddisc brakes, from the master cylinder, undiminished. One of the reasonsfor proportioning the pressure in this manner is that increased brakingpressure may be applied to disc brakes without locking the brakes whichis not true of shoe type brakes. Thus the point at which the hydraulicpressure rate 1ncrease, going to the shoe type brakes, should taper off,is one that must be picked for each individual system dependent upon thesurface area of the shoes and other well known factors. In the presentinstance, the proportioning valve 20 programs the decrease in hydraulicpressure rate to the rear brakes 13. As hydraulic pressure increases,the spool 26 gradually moves to the right until it reaches a positionclosing off the first chamber 28. To this end, the inlet end 26a of thespool 26 has a nose cone 48 connected thereto, which nose cone includesa conical or tapered lip portion 49 for seating in a like conical seat30a in the passage 30 of the sleeve 27.

As set forth in the copending application, the nose cone 48 comprises acylindrical insert 50 connected to one end of the spool 26, in thepresent instance force fitted inside a cylindrical receiving chamber 51,and having interiorly mounted therein a stiffening member 52. (See FIG.3.) It should be noted that the stiffening member 52 has a leading edge52a spaced axially and interiorly of the conical lip. 49 of thecylindrical insert 50. Preferably the cylindrical insert 50 isconstructed of a stiff yet resilient material such as nylon, while thestiffening member 52 is preferably composed of a material that ishydraulically transparent to support the cylindrical insert 50. Such ahydraulically transparent material is sintered porous bronze which tendsto restrain the cylindrical insert 50 upon contact of the tapered lip 49with its associated seat 30a in the sleeve 27, while permitting thepressure to act on the internal diameter of the cylindrical insert andthus aid the sealing action of the lip 49 against the seat 30a.

When the spool 26 is in its second position (i.e. to the right) andthenose cone 48 is positioned in the seat 30a of the sleeve 27, asillustrated in FIGS. 2 and 3, a different area, designated in thepresent instance A-3, is exposed to the hydraulic pressure from themaster cylinder 16. In the present instance, the area A-3 is less thaneither the area A-1 or A-2, whereby, after the valve has reached thesecond position, the pressure at the outlet 23 will remain at thepressure which causes the spool 26 to reach the second position, plusthe ratio of A-32A-1 times the difference between the new hydraulicpressure at the inlet 22 and the pressure of closing.

The check valve Inorder that the conduit 32 is sealed off upon the spool26 reaching its second position and the nose cone 48 being seated in theseat 30a of the sleeve 27, and at the same time to provide means forpermitting a rapid decrease in the fluid pressure at the rear brakeshoes upon release of the foot pedal 19a, novel sealing means in thepresent instance a check valve 60, is provided interiorly of thestiffening member 52 and positioned to close off the conduit 32.

As illustrated in FIG. 2, when the spool 26 is in its first positionhydraulic pressure may reach the conduit 32 through the radiallyextending apertures 3211 which communicate with the chamber 28. However,when the spool is in its second position and the nose cone 48 is seatedin its seat 30a of the sleeve 27, the sealing means 60 must be operativeto preventfluid or hydraulic pressure from communicating through theextension 32b of the conduit 32. To this end,,the check valve comprisesresilient ball 61, in the present instance composed of ethylenepropylene and having a hardness of approximately 70 durometers, isflotably mounted in the stifiening member 52. The resilient ball 61 isloosely contained in a pocket 62 diverging tapered. splines, in thepresent instance three having angulated splines 63 diverging axiallyoutward away from the inlet. As illustrated in FIGS. 3 and, 4,stiifening memher 52 contains lands 64 and axially extending grooves 65,the radially diverging or angulated splines 63 being formed at theterminus of the lands 64. In this manner the splines 63 limit the axialmovement of the resilient ball 61 in the stiffening member 52.

In order to prevent wedging of the ball 61 against the splines 63, whileat the same time limiting the movement of the ball axially of thestiffening member 52, the included angle between the splines shouldpreferably be not less than 20 and not greater than 180. An includedangle between the splines of less than 20 may cause wedging of theresilient ball 61 within the splines while an included angle of 180would allow the ball to move radially within the stiffening member 52and prevent it from properly seating in the conduit extension 32b. Inthe present instance, in the range of pressures normally encountered ina hybrid brake system of the afore-mentioned type as well 'as theproperties of the material of which the ball is fabricated, an includedangle of approximately 40 limits the axial movement of the ball and atthe same time helps center the ball to insure proper seating in theconduit extension 32b.

It should be recognized that in systems encountering lower pressure orcontaining a different liquid, i.e. other than a hydraulic brake fluid,a resilient ball having a different composition and physical propertiesmay be used. In addition, the properties of the ball may permitvariation in the angular relationship between the splines.

To prevent excessive wear on one surface of the resilient ball 61, andat the same time to automatically permit a new seating surface to beexposed to the conduit extension 32b, upon release and reapplication ofpressure to the inlet 22 from the master cylinder 18, it is desirable tooffset the splines 63 axially of the stiffening member 52. Such anembodiment is illustrated in the development of FIG. 5 wherein theleading edge of the spline is offset axially of the stiffening member 52by the angle theta. In this manner upon release of the brake pedal 19athe pressure on the portion of the ball exposed to the conduit 32overcomes the inlet pressure causing the ball to unseat and move intothe pocket 62. By axially offsetting the splines, the ball will strikeone of the splines earlier than the others which creates a rollingeffect which will cause the ball to incur a new seating surface in theconduit 32 upon reapplication of brake pressure in the entry 22.

Thus the present invention provides a check valve which due to its freemovement and special design insures proper seating of the valve whilesubstantially decreasing the opportunity for dirt or other impurities tohang up on the valve seat and cause improper functioning of theproportioning valve with which it is associated.

Thus although the invention has been described with a certain degree ofparticularity, it should be understood that the present disclosure isonly exemplary of the invention, and that numerous changes in thedetails of construction, and the combination and arrangement of partsmay be made without departing from the spirit and scope of the inventionas hereinafter claimed.

In the claims:

1. In a hydraulically operated proportioning valve comprising a bodyhaving hydraulic fluid inlet means and hydraulic fluid outlet means;spool means movable between a first position adjacent said outlet and asecond position adjacent said inlet; connecting means interiorly of saidspool to permit hydraulic communication between said outlet and saidinlet when said spool is in its first position, said spool having aproportioning ratio between the end thereof exposed to said outlet andthe end thereof exposed to said inlet such that the hydraulic forceexerted on said spool at said outlet is greater than the hydraulic forceexerted upon said spool at said inlet: and sealing means operative toseal said connecting means when said spool is in its second position andto release and permit fluid communication thereby upon release ofhydraulic pressure at said inlet; said sealing means comprising a checkvalve means including a pocket in said spool means adjacent said inletand communicative with said inlet and said connecting means, said pockethaving angulated splines diverging axially outward away from said inletand a resilient ball loosely constrained in said pocket, operative, whensaid spool is in the second position, upon a greater pressure beingexerted at said inlet than at said outlet to seal said connecting means,and upon an increased pressure being exerted at said outlet than at saidinlet to permit fluid communication between said connecting means andsaid inlet.

2. In a hydraulically operated proportioning valve in accordance withclaim 1 wherein said splines of said pocket limit the axial movement ofsaid ball in said pocket towards said inlet, and a seat for said ballconnected to and adjacent said connecting means.

3. In a hydraulically operated proportioning valve in accordance withclaim 2 wherein at least one of said splines is axially offset to imparta rolling motion to said ball upon release of pressure at said inlet.

4. In a hydraulically operated proportioning valve in accordance withclaim 1 wherein said spool includes biasing means connected theretomaintain said spool in the first position prior to the application ofhydraulic pressure to said inlet, sleeve means circumscribing the inletend of said spool and defining a chamber having a passage therein whichcommunicates with said inlet, and a seat in said sleeve; including anose cone on the inlet end of said spool; said nose cone having alipportion to engage said seat in said chamber to seal said chamber whensaid spool is in its second position, and comprising a hollowcylindrical member connected to said spool and a tubular stiffenerinserted in said member having a leading edge lying closely adjacentsaid lip of said cone and axially spaced interiorly of said member, andlands and grooves in said stiffener and axially thereof terminating insaid diverging splines forming said pocket.

5. In a proportioning valve in accordance with claim 4 wherein saidsplines are axially offset whereby upon release of hydraulic pressure atsaid inlet said ball moves in said pocket striking one spline prior tostriking the other spline causing said ball to rotate, thus exposing anew seating portion for said ball upon reapplication of pressure.

6. In a proportioning valve in accordance with claim 5 wherein saidstiffening member is composed of a hydraulically transparent materialand said hollow cylindrical member is stiff yet resilient.

'7. In a proportioning valve in accordance with claim 2 wherein saidball is composed of ethylene propylene having a hardness ofapproximately 70 durometers.

8. In a proportioning valve in accordance with claim 2 wherein theincluded angle between said splines forming said pocket is between 20and References Cited UNITED STATES PATENTS Re. 22,180 9/ 1942 Otis137512.2 2,529,731 11/1950 Hollerith 137-509 2,991,797 7/1961 Baldwin3036 XR 3,163,473 12/ 1964 Stelzer 303-6 FOREIGN PATENTS 969,901 9/ 1964Great Britain.

M. CARY NELSON, Primary Examiner.

R. I. MILLER, Assistant Examiner.

